AlgoSolveoRoadmap › Stage 2: Arrays & Strings › Pattern 11 of 53
DSA pattern guide
Strings — Sliding Window
Substring with all/at most/no repeating characters, anagrams inside a string.
Use it when
Substring with all/at most/no repeating characters, anagrams inside a string.
Key idea
Window plus a character count map. Expand right, shrink left until the window is valid again.
Practice problems, in order
- Find All Anagrams in a StringMedium
- Longest Substring Without Repeating CharactersMedium
- Permutation in StringMedium
- Minimum Window SubstringHard
- Substring with Concatenation of All WordsHard
How to practise this pattern
- Read the problem and look for the signal above before writing any code.
- Say the brute force out loud, with its time complexity, then ask what work it repeats.
- Apply the key idea and write the optimised version yourself.
- If you're stuck for more than 10 minutes, take one small hint, not the full solution.
- Move to the next problem only when you can explain why this pattern fits.
Stuck on one of these?
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